Bring a large pot of salted water to a boil. In a medium bowl, toss the shrimp well with the ½ teaspoon salt and the baking soda. Set aside.

In a large skillet or sauté pan, heat 4 tablespoons olive oil over medium-high heat until shimmering. Add reserved shrimp shells and cook, stirring constantly, until they've all turned a reddish color, about 4 minutes. Off the heat, remove shells using tongs, a slotted spatula, and/or a slotted spoon, allowing any excess oil to drain back into skillet as you go; discard shells. You should still have plenty of oil left in the skillet.

Return skillet to medium-high heat, add shrimp, and cook, stirring and turning occasionally, until shrimp are just starting to brown in spots and are almost fully cooked through, about 3 minutes. Off heat, transfer shrimp to a plate and set aside.

Return skillet to medium-low heat. Add garlic, oregano, and chile flakes and cook, stirring, until garlic is just beginning to turn golden, about 3 minutes. Add brandy, if using, and cook until almost fully evaporated. Add tomatoes and clam juice and bring to a simmer. Season with salt.

Boil pasta in a pot of salted water until al dente. Drain, reserving about 1 cup of pasta cooking water, and add pasta to the sauce along with a splash of pasta cooking water. Add shrimp and cook over medium-high heat, stirring, until sauce reduces and clings to pasta and shrimp are fully heated through; add more pasta water as necessary if the sauce becomes too dry. Season with salt, if necessary.

Stir in parsley and remaining 2 tablespoons olive oil. Serve right away.